Power to various components of an electronic system, such as a computer system or other type of electronic system, is provided by a power supply in the electronic system. The power supply includes a power source, which can include an alternating current (AC) source, such as that provided by wall power outlets. Typically, the AC power source is provided to an input of an AC power adapter or AC/DC power supply, which converts the AC input to a direct current (DC) output voltage provided to an electronic system. Another type of power source for an electronic system is a battery, which provides one or more output DC voltages for the electronic system.
The power supply of an electronic system also includes one or more DC-DC converters for converting an input DC voltage (such as that provided by a battery or by the AC power adapter or AC/DC power supply) to one or more output (usually different) DC voltages that are used to power the components of the electronic system.
Some DC-DC converters include a pulse-width modulation (PWM) circuit that controls the duty cycle of a switch in the converter to regulate the output DC voltage. The duty cycle of the switch refers to the amount of time that the switch is on versus the amount of time that the switch is off. For example, a 10% duty cycle means that the switch is on 10% of the time and off 90% of the time. Typically, the PWM circuit of the converter varies the duty cycle of the switch in response to fluctuations in the output DC voltage of the converter. By adjusting the duty cycle, more or less energy can be delivered so that the output voltage can be increased or decreased as appropriate.
The output DC voltage from the converter at a load is fed back into a sense input of the converter (in a converter's voltage loop), so that the converter is able to detect the output voltage at the load. Variations in a load condition can cause the output DC voltage to vary. In response to variations in the sensed voltage at the sense input, appropriate adjustments can be made in the converter to maintain the output voltage at the load within desired limits. As noted above, the output voltage from the converter can be adjusted by varying the duty cycle of the PWM circuit.
The converter voltage loop described above adjusts for variations in the output DC voltage at the load is a relatively slow process (usually 2-3 microseconds). As a result, the converter may not be able to compensate for variations in the output voltage in a timely manner. The result may be dips or spikes in the output DC voltage at the load, which can cause certain components to fail or experience errors. As supply voltages to low-voltage components, such as application-specific integrated circuit (ASIC) devices, field programmable gate array (FPGA) devices, and so forth, continue to decrease (such as to 1.5 volts or lower), even small variations in a converter output DC voltage can cause errors in the low-voltage components.
The regulation of the output DC voltage at the load is also dependent upon the accuracy in the initial set point of the converter. The initial set point refers to the intended or designed output voltage level of the converter under specified load conditions, usually controlled by the sense inputs of the converter.